Light is amazing.

It is a wave and a particle at the same time.

Light (and in fact the entire visible and invisible electromagnet spectrum) travels at the same speed through a vacuum; 186,000 miles/second.

Light is effectively invisible until it reflects off of something and into our eyes. We don’t see light waves flashing across our paths, we only see what is reflected into our eyes.

Short wavelength visible light is blue and has a higher energy so it scatters more in the atmosphere making the sky blue. But as the sun sets near the horizon the blue light is scattered away through the greater amount of atmosphere between the horizon and our eyes, and we only see the redder light.

Things don’t have a colour, they just reflect certain wavelengths of light. Something which appears blue is just reflecting blue light and absorbing all the rest. It’s not actually blue.

Because light from the sun takes 8 minutes to reach us, the sun actually rises 8 minutes before we see it.

A single photon of light can travel through two parallel slits simultaneously. This is very weird.

Only 1 billionth of the sun’s light reaches earth. But the sun itself consumes nearly 5 million tones of its mass every second to produce it. About 1.3 million earths could fit inside the sun but the biggest stars would fill half of our solar system if they were at the centre. Their light which we see today left them maybe a billion years ago or more.

The eye is an extension of the brain. Once triggered/fired by a light photon, a photoreceptor cell in the human retina chemically refreshes itself in milliseconds and is ready to fire again. The eye doesn’t actually see light it just sends electrical signals to the visual cortex in the brain which does all the figuring out and then presents itself with what we then think is an image.

It also helps me locate the fridge.

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@divegeester said
Sure.

Thread 199353

@divegeester said

Because light from the sun takes 8 minutes to reach us, the sun actually rises 8 minutes before we see it.

@ponderable said
Actually it doesn't. "Rising of the sun" is from earth perspective...

@david-burton said
so let me get this right if you are driving your car at the speed of light and you turn your headlight on ......nothing happens ?

@divegeester said
No idea.

Anything with any mass cannot travel at the speed of light anyway. So it couldn’t happen.

@david-burton said
so if light has 0 mass why cant it escape a black hole? and surely sun rise is the motion of the earth not the sun actualy moving or amI wrong?and light even with 0 mass can be bent in a vacum.

@david-burton said
so let me get this right if you are driving your car at the speed of light and you turn your headlight on ......nothing happens ?

@divegeester said
Light is amazing.

It is a wave and a particle at the same time.

Light (and in fact the entire visible and invisible electromagnet spectrum) travels at the same speed through a vacuum; 186,000 miles/second.

Light is effectively invisible until it reflects off of something and into our eyes. We don’t see light waves flashing across our paths, we only see what is ...[text shortened]... brain which does all the figuring out and then presents itself with what we then think is an image.

A photon checked into a hotel.
The porter offered to carry his bags.
He replied 'its ok, I'm travelling light.'

A few years ago Stamford University slowed light down to 27mph.
Then Harvard slowed light down to zero.